Device comprising a gaseous glowdischarge tube



Oct. 23, 1962 s. M. FRouws 3,069,340

' DEVICE COMPRISING A GASEOUS GLOW-DISCHARGE- TUBE Filed July 15, 1960 2Sheets-Sheet 2 INVENTOR BY amkmfdz' AGENT Unite This invention relatesto devices comprising a gaseous glow-discharge tube having, in additionto a main cathode and a main anode, at least one auxiliary anode and inwhich a primer discharge shielded relative to the main discharge path ismaintained in order to prevent delays in ignition, an atomised metalliclayer being present on the wall of the tube. The invention also relatesto gaseous glow-discharge tubes intended for such devices.

In tubes of the above-mentioned kind having on their wall an atomisedmetallic layer originating from the electrodes, wall charges may giverise to spontaneous initiation of the main discharge, more particularlyif the potential of the wall charge is increased due to external causes.The conductive metallic layer on the wall permits of initiating adischarge more readily than in the absence of such an atomised metalliclayer, since due to the conductive layer the charge of the whole surfaceof the wall can be carried away.

Due to the presence of a primer discharge, wall charges may readilyoccur due to diffusion of charge carriers to the wall which thus canassume a potential which is only little less, namely not more thanseveral tens of volts, than the potential of the anode of the primer discharge.

An object of the invention is to provide steps which permit ofpreventing interference due to the presence of wall charges.

According to the invention, in a device comprising a gaseousglow-discharge tube having, in addition to a main anode and a maincathode, at least one auxiliary anode and wherein a primer dischargeshielded relative to the main discharge path is maintained in order toprevent delays in ignition, whilst an atomised metallic layer is presenton the wall of the tube, the auxiliary anode has a shape such that partthereof co-acts with the cathode for bringing about an auxiliarydischarge, the auxiliary anode having a peak extending up to so short adistance from the Wall of the tube that, upon increasing potential ofthe coating on the wall and at a low potential of the auxiliary anode,the wall charge flows off towards the peak of the auxiliary anodewithout resulting in a decreaseof the igniting voltage in the maindischarge path.

With the invention it is ensured that wall charges cannot bring about adischarge, for example, towards the cathode or towards a portion of theauxiliary anode such that the main discharge is initiated, since incircuits having glow discharge tubes, when in the rest condition, theauxiliary anodes usually have cathode potential or a potential which isseveral tens of volts lower.

The step according to the invention is important more particularly ifthe tube contains two auxiliary anodes which consist, like the cathode,of molybdenum. In the case of two auxiliary anodes, it is substantiallyunavoidable to make then from similar material to that of the cathodefor which molybdenum is chosen on account of its favourable dischargetechnical properties. In fact, when the main discharge has been ignitedby one auxiliary anode, the other auxiliary anode which, owing to itsconnection, is at cathode potential or a lower potential also draws partof the current, resulting in this auxiliary anode being somewhatatomised. If

Bfihhfiifi Patented Oct. 23, 1962 the auxiliary anode consists of adifferent material from that of the cathode, then in the vicinity ofthis auxiliary anode the cathode will be somewhat covered with auxiliaryanode material which is not atomised immediately by the main dischargeburning on another portion of the cathode. The covering of the cathodewith material of the auxiliary anode results in a modification of theproperties of the cathode and more particularly of the igniting voltage.It is therefore necessary for the auxiliary anode to be manufactured ofsimilar material to that of the cathode. Since molybdenum has a low workfunction and hence, as a cathode in a discharge path, a low ignitingvoltage, sparks readily pass over from the charged coating on the walltowards an arbitrarily shaped auxiliary anode of molybdenum, thusresulting in ignition of the main discharge. It will be evident that theuse of the particular shape of the auxiliary anode according to theinvention is of special importance if the tube has a molybdenum cathodeand two auxiliary anodes likewise of molybdenum.

In order that the invention may be readily carried into effect, it willnow be described in detail, by way of example, with reference to theaccompanying diagrammatic drawings, in which:

FIGURE 1 is a perspective elevational View of a gaseous glow-dischargetube, partly broken up, according to the invention.

FIGURE 2 shows a circuit comprising a plurality of such tubes.

FIGURE 1 shows the glass wall 1 of the tube, which is partly broken up,and a base 2. A ceramic tube 3 surrounds a lead-through pin 4 to which acathode 5 is soldered with the aid of a bent tongue. The cathode has arounded edge 6 to prevent ignitions from a coating 12 on the walltowards the cathode. An anode 8 of the tube is positioned somewhateccentrically. Below the anode 8 a metal strip 9 is provided on alead-through pin. During the operation of the tube, the strip 9 isconnected to the cathode lead through so high-ohmic a series-resistorthat a current of about Srnicroamps flows between the anode 8 and thestrip 9. The charge carriers diffusing from this weak discharge towardsthe main discharge path prevent therein the occurrence of delays inignition, but without giving rise to decreases in the igniting voltage.The cathode 5 has pointed projections 7, one on each side and oppositeeach projection is a plate-shaped auxiliary anode 10. The auxiliaryanodes Ill are likewise mounted on lead-through pins surrounded byceramic tubes. Each auxiliary anode has a sharp peak 11 as a projectionwhich extends up to a distance of about 0.4 mm. from the metal layer 12present on the wall 1. The metal layer is produced in forming theelectrodes by means of intense discharges for cleaning more particularlythe cathode surface, resulting in material at'omisation.

If wall charges occur as a result of diiiusion of charge carriers fromthe primer discharge, the coating 12 on the wall may acquire a potentialwhich can easily be 200 volts for an anode voltage of 250 volts. In therest condition of the circuit, the auxiliary anodes 10 are at cathodepotential or at a lower potential. With the small distance between thepeaks 1]. and the Wall coating 12, this may give a rise to a weakdischarge between one of the peaks l1 and the coating 12. Since the areaof discharge are comparatively far remote from the main discharge pathbetween the electrodes 5 and 8, these weak discharges do not bring abouta decrease in igniting voltage and certainly do not bring about ignitionin the main discharge path. The discharges between ll and 12 may occurmore or less continuously or, for example, only if the potentialof thecoating 12 rises due to external electrostatic influences.

u The envelope has an outer diameter of 9.5 mms. Due to this small size,it is substantially impossible to provide a contact with the coating onthe wall, which contact would still be doubtful without particularsteps. A strong contact pressure would otherwise impede mechanicalsealing of the base into the bulb. Due to the small diameter of thetube, the use of large numbers of tubes in printed circuits is possible.

FIGURE 2 shows a portion of a counting circuit comprising gaseousgloW-discharge tubes according to the invention. The first glowdischarge tube shown, indicated by 21, has a cathode 22 an anode 23,auxiliary anodes 24 and 25, a primer discharge cathode 26 and a coating27, shown in a broken line, on the wall. Reference numerals 31 to 37 areused for the second tube. The tube 21 is preceded by a tube 11 and thetube 31 is followed by tubes 41, 51 etc., which tubes are not shown.Each tube has associated with it a cathode resistor 102, bridged by acapacitor 103. Each of the primer cathodes 26, 36 etc., is connectedthrough a high-ohmic resistor 105 to the cathode lead. A common cathoderesistor is indicated by 101. Each of the auxiliary anodes 24, 34, etc.is connected through a resistor 104 to the cathode of the preceding tubeand through a capacitor 107 to an input lead 106. Each of the auxiliaryanodes 25, 35, etc. is connected through a resistor 108 to the cathodeof the next-following tube and also through a capacitor 109 to an inputlead 110.

When it is assumed that a discharge takes place in the tube 21, tube 31is ignited if a positive pulse of sufficient strength occurs across thelead 106, since the auxiliary anode 34 already takes a positive biassingpotential from the cathode resistor 102 of tube 21. Tube 41 is ignitedupon a subsequent pulse across the lead 106.

If, however, it is assumed that the discharge takes place in tube 31,tube 21 is ignited if a positive pulse of suflicient strength occurs atthe lead 110 and tube 11 is ignited upon a subsequent pulse. The circuitis thus suitable for moving the discharge in two directions or, since itis used as a counting circuit, for adding and for subtracting. Due tothe presence of the coatings 2 7, 37, etc. on the walls of the tubes,interference might occur which is prevented, however, by the auxiliaryanodes of particular shape and configuration as shown in FIG- URE 1.

What is claimed is:

1. A glow-discharge tube comprising an envelope containing an ionizablegaseous medium therein at a pressure suflicient to initiate and maintaina glow-discharge, spaced apart main anode and cathode electrodespositioned in said envelope defining a main discharge path therebetween,a coating of a low work-function material on the inner wall of saidenvelope, a trigger electrode spaced from the main cathode electrode andhaving a projection positioned closer to the coating on the inner wallof said envelope than any other portion thereof for initiating adischarge between the wall coating and the trigger electrode when thewall coating assumes a given potential due to charge accumulationsthereon, and a priming cathode located outside of and shielded from themain discharge path between the main anode and cathode for producing apriming discharge with the main anode which charges the coating on theinner wall of the envelope to a given potential relative to the maincathode.

2. A glow-discharge tube comprising an envelope containing an ionizablegaseous medium therein at a pressure sufficient to initiate and maintaina glow-discharge, spaced apart main anode and cathode electrodespositioned in said envelope defining a main discharge path therebetween,a coating of a low work-function material on the inner wall of saidenvelope, a pair of trigger elec trodes spaced from the main cathodeelectrode, each of said trigger electrodes having a projectionpositioned closer to the coating on the inner wall of said envelope thanany other portion thereof for initiating a discharge between the wallcoating and at least one of the trigger electrodes when the wall coatingassumes a given potential due to charge accumulations thereon, and apriming cathode located outside of and shielded from the main dischargepath between the main anode and cathode for producing a primingdischarge with the main anode which charges the coating on the innerwall of the envelope to a given potential relative to the main cathode.

3. A glow-discharge tube comprising an envelope containing an ionizablegaseous medium therein at a pressure sufiicient to initiate and maintaina glow-discharge, spaced apart main anode and cathode electrodespositioned in said envelope defining a main discharge path therebetween,said cathode having at least a surface layer of a material of lowwork-function, a coating on the inner wall of said envelope of the samematerial as the surface layer of the cathode, a trigger electrode spacedfrom the main cathode electrode and having a projection positionedcloser to the coating on the inner wall of said envelope than any otherportion thereof for initiating a discharge between the wall coating andthe trigger electrode when the wall coating assumes a given potentialdue to charge accumulations thereon, and a priming cathode locatedoutside of and shielded from the main discharge path between the mainanode and cathode for producing a priming discharge with the main anodewhich charges the coating on the inner wall of the envelope to a givenpotential relative to the main cathode.

4. A glow-discharge tube comprising an envelope containing an ionizablegaseous medium therein at a pressure sufficient to initiate and maintaina glow-discharge, spaced apart main anode and cathode electrodespositioned in said envelope defining a main discharge path therebetween,said cathode having at least a surface layer consisting of molybdenum, acoating of molybdenum on the inner wall of said envelope, a triggerelectrode spaced from the main cathode electrode and having a projectionpositioned closer to the coating on the inner wall of said envelope thanany other portion thereof for initiating a discharge between the wallcoating and the trigger electrode when the wall coating assumes a givenpotential due to charge accumulations thereon, and a priming cathodelocated outside of and shielded from the main discharge path between themain anode and cathode for producing a priming discharge with the mainanode which charges the coating on the inner wall of the envelope to agiven potential relative to the main cathode.

5. A glow-discharge tube comprising an envelope containing an ionizablegaseous medium therein at a pressure sufficient to initiate and maintaina glow-discharge, spaced apart main anode and cathode electrodespositioned in said envelope defining a main discharge path therebetween,said cathode having at least a surface layer consisting of molybdenum, acoating of molybdenum on the inner wall of said envelope, a triggerelectrode spaced from the main cathode electrode, said trigger electrodehaving at least a surface layer of molybdenum and having a projectionpositioned closer to the coating on the inner wall of said envelope thanany other portion thereof for initiating a discharge between the wallcoating and the trigger electrode when the wall coating assumes a givenpotential due to charge accumulations thereon, and a priming cathodelocated outside of and shielded from the main discharge path between themain anode and cathode for producing a priming discharge with the mainanode which charges the coating on the inner wall of the envelope to agiven potential relative to the main cathode.

Peck July 10, 1951 Thomas Feb. 26, 1957

